Project Summary Mind-body interventions decrease state arousal in a variety of settings and populations,1-10 which presents a novel scientific and public health opportunity for use in a harm reduction framework. Evening media use in youth is a significant risk for sleep problems,11-17 largely mediated by increased state arousal.17,18 Eliminating media use is neither feasible at a public health level nor perhaps even desirable given the role it plays in the lives of youth and adults,19 but mind-body interventions have the potential to mitigate state arousal effects and thus reduce negative impacts on sleep. Given emerging literature on links between intensive media use, sensory and interoceptive awareness, and self-regulation, we propose to study two related mind-body approaches: mindfulness sensory awareness exercises to increase sensory and interoceptive awareness,20 and mindful body awareness check-ins to guide media use choices. In order to optimize this approach, we will examine the effects of these mind-body strategies independently, jointly, and in combination with other strategies to mitigate the effects of media use on sleep, including amber glasses to block short wavelength light during evening media use, avoiding content with high vigilance demands or violence, and external controls to time-out media access. Prior studies are limited by unrealistic interventions, artificial setting, exposure classification, and subjective measures,21 leaving important but closeable gaps in the science. Direct measurement of state arousal in youth in the ecologically valid home environment via heart rate variability, electrodermal activity, and self-report in youth in a mind-body intervention is highly innovative. Given the high prevalence evening media use, the known short and long-term adverse sequelae of sleep problems, and the lack of current intervention strategies acceptable to youth, the proposed research also has the potential for strong and broad public health impact. Next steps require a deeper understanding of the mechanistic effects of state arousal in interventions to mitigate the harm of media use. We will employ a Multiphase Optimization Strategy (MOST), an innovative, evidence-based approach to using rigorous, experimental methods to optimize multicomponent behavioral interventions prior to evaluation, making it especially appropriate for the R61/R33 mechanism and the proposed intervention. In the R61, we will use an experimental crossover design in a 26-2 fractional factorial matrix to optimize the mechanistic efficacy of the intervention, and a 3- arm randomized trial in the R33 to use those findings to optimize intervention effectiveness. Both phases will enroll youth age 10-14 years with evening media use most nights and behavioral sleep problems.